1. Technical Field
The present invention relates to liquid ejecting heads and liquid ejecting apparatuses. More specifically, the present invention relates to inlet geometry for the liquid supply channels for an inkjet head.
2. Related Art
An ink ejecting head that ejects liquid ink is one type of liquid ejecting head. Generally speaking, an ink ejecting head includes a manifold, pressure generating chambers, and nozzles. The ink ejecting head receives a supply of ink from an ink holding unit, such as, for example, an ink cartridge. The ink is sent from the ink cartridge to the manifold, then to the pressure generating chambers through ink supply channels, which connect the single manifold to the multiple pressure generating chambers. The ink is then ejected to the exterior through respective ones of the nozzles, via respective ink discharge channels, from the pressure generating chambers, which have been pressurized as the result of the driving of respective pressure generating elements. This can be seen in, for example, JP-A-2001-219560.
It has been confirmed that bubbles can sometimes be undesirably produced in the liquid within the manifold, because extremely small dissolved gaseous bodies within the liquid expand due to rises in the temperature of the liquid, drops in atmospheric pressure, and so on, and the expanded gaseous bodies then appear as bubbles. This can be problematic, because even a very small number of bubbles can block the liquid from being ejected through the nozzles.
The following explanations must not be considered as limiting the scope of the invention in any respect whatsoever.
When bubbles form, the bubbles tend to, for the most part, move along with the liquid from the ink cartridge into the manifold, toward the liquid supply channels. In the case where the bubbles that have been produced are too large to be sucked into the liquid supply channels, those bubbles cover the inlets of the liquid supply channels. As a result, the flow of the liquid from the manifold to the pressure generating chambers is cut off. In this state, if the driving of the pressure generating elements is continued in a state where the flow of the liquid from the manifold to the liquid supply channels has been cut off, the air can build up within the pressure generating chambers.
When the air has built up, the pressure generating elements can generate an insufficient amount of pressure within the pressure generating chambers to eject the liquid through the nozzles. If the liquid is not ejected through the nozzles, the flow of liquid from the liquid supply channels to the pressure generating chambers stops, and the suction on the bubbles that are covering the liquid supply channels from the liquid supply channel toward the pressure generating chambers stops as well.
Meanwhile, in the manifold, liquid flows toward the liquid supply channels that are not covered by the bubbles. Accordingly, due to the momentum of the liquid flow toward the liquid supply channels that are not covered by bubbles, the bubbles that cover the liquid supply channels are sucked toward the inlets of the liquid supply channels that are not covered by the bubbles. The inlets of the liquid supply channels toward which the bubbles have been sucked are then covered by the bubbles.
As described above, the flow of liquid can be cut off from the liquid supply channels that have been newly covered by the bubbles, and the liquid is therefore not ejected through the nozzles. Meanwhile, the liquid supply channels that were covered by bubbles before the bubbles moved have air built up within the pressure generating chambers. Accordingly, even if the pressure generating elements are driven, the liquid cannot flow from the liquid supply channels toward the nozzles. Accordingly, as described earlier, the bubbles move from one liquid supply channel to another liquid supply channel, thus continually increasing the number of nozzles through which liquid is not ejected, which results in liquid not being ejected simultaneously through multiple nozzles.
Note that this issue is not limited to ink heads that eject ink as their liquid; the same issue also arises in liquid ejecting heads capable of ejecting a liquid aside from ink.